while i still think that a processor error is the most reasonable thing i can come up with, neither disabling the dep nor turning off the multicore made any effect.
i've been testing old files and have yet to produce a similar error. remember: this doesn't happen with every eq decision. nor does there really appear to be a discernible pattern regarding which ones it happens with.
i've also experimented a little with saving mixer settings and it does not seem to affect the outcome, which suggests the error must be in the save process rather than the mixer. otherwise, i could wipe the mixer and reload. but that's not working.
if i can't determine a problem in any of the previous files, i'm left to conclude that there's something very strange with these specific files. i may have to temporarily move to sonar or reaper to finish this project.